1. Field of the Invention
The present invention relates to a stereoscopic-endoscope display control apparatus and a stereoscopic endoscope system which permit stereoscopic viewing using a stereoscopic endoscope.
2. Description of the Related Art
In general, endoscope systems for endoscopic surgery under observation using an endoscope are widespread.
According to stereoscopic endoscope systems using a stereoscopic endoscope having stereoscopic vision, stereoscopic observation can be performed, thus providing such an environment that surgery can be smoothly performed even when the surgery requires exacting tasks.
A stereoscopic endoscope picks up right and left images having a parallax using right and left optical systems. In this case, the distance between an object and objective lenses where right and left object images match with each other (except the difference therebetween due to a parallax) is in advance designed in the stereoscopic endoscope. If the distance therebetween is shifted from a design point, the display positions of the object displayed in a display element differ therebetween.
The difference between right and left points of view recognized in the brain allows a human being to perceive the depth and dimension of an object in view. Thus, stereoscopic viewing can be ensured. FIG. 18 shows the schematic structure of a conventional stereoscopic endoscope system 90.
The stereoscopic endoscope system 90 includes a stereoscopic endoscope 91, camera control units (hereinbelow, abbreviated to CCUs) 93L and 93R for processing image pickup signals obtained by the CCDs 92L and 92R arranged in the stereoscopic endoscope 91, and display elements 94L and 94R for displaying video signals generated by the CCUs 93L and 93R.
At the distal end of the stereoscopic endoscope 91, objective lenses 95L and 95R are laterally arranged at a distance from each other. Each objective lens receives light from an object located in the front of the lens and forms an image on the corresponding CCD 92L or 92R arranged in the rear of the lens via a group of relay lens (not shown).
The observation distance between an object and the stereoscopic endoscope 91 varies. The stereoscopic endoscope 91 is designed, referring to FIG. 18, when the object is located at a position B, images are respectively formed in the centers of the CCDs 92L and 92R such that the images present the same state (the images match with each other) except the difference therebetween due to a parallax. The images in the same state are displayed in the display elements 94L and 94R, respectively. In other words, actually, there is a parallax, so that the difference caused by the parallax permits stereoscopic viewing (stereopsis).
FIG. 19 shows areas where observation states vary depending on the setting states of the objective lenses 95L and 95R. As shown in FIG. 19, there are an areas that is observed by the objective lens 95R but is not observed by the objective lens 95L and another area which is observed by the objective lens 95L but is not observed by the objective lens 95R.
Accordingly, observed images displayed in the left and right display elements 94L and 94R are as shown in FIGS. 20A to 20C. FIG. 20A shows observed images obtained when the object is located in a position A. FIG. 20B shows observed images obtained when the object is located in the position B. FIG. 20C show observed images obtained when the object is located in a position C.
Referring to FIGS. 20A to 20C, when the object is located in the position A or C such that the distance from the objective lenses is different from the distance between the position B and the objective lenses, there is an area that is displayed in the right display element 94R but is not displayed in the left display element 94L and another area that is displayed in the left display element 94L but is not displayed in the right display element 94R.
Japanese Unexamined Patent Application Publication No. 6-261860 discloses a system including parallax control means arranged in a stereoscopic endoscope in order to solve a feeling of strangeness in stereoscopic viewing.